Electromagnetic motor

ABSTRACT

An electromagnetic stepping motor has a stator assembly comprising two pieces. These two pieces are assembled to each other by a protrusion of cylindrical shape of one of the pieces which engages in a recess, of corresponding shape, in an extension of the other piece. The two pieces, which are of elongated general shape, are disposed parallel to each other with said one piece constituting the core of an energizing coil of the motor. The coil can be wound directly on to the piece of the stator constituting the core of the coil.

BACKGROUND OF THE INVENTION

a. Field of the invention

The present invention relates to a stepping electromagnetic motor of thetype having a stepping, rotor, and a stator which is made of at leasttwo pieces.

b. Description of the Prior Art

The known electromagnetic motors of the above mentioned type comprise,most usually, a core passing through an energizing coil of the motor.This core is terminated at each of its ends by an ear-shaped portion. Oneach ear-shaped portion there is secured a corresponding end of one ofthe two other pieces of the stator. Each of the two other pieces of thestator terminates, at its opposite end, in an enlarged pole face.

This arrangement has the drawback that all the pieces of the stator arenot in the same plane. In other words, the axis of the core of the coilof the motor, that is to say the axis of the coil, is not situated inthe median plane of the stator. Moreover, a good contact is not alwaysachieved between the ears of the core and the secured ends of the twoother pieces of the stator, a gap or interface often subsisting betweenthe two contact surfaces.

SUMMARY OF THE INVENTION

The various features of the invention will be apparent from thefollowing description, drawings and claims, the scope of the inventionnot being limited to the drawings themselves as the drawings are onlyfor the purpose of illustrating ways in which the principles of theinvention can be applied. Other embodiments of the invention utilisingthe same or equivalent principles may be used and structural changes maybe made as desired by those skilled in the art without departing fromthe present invention and the purview of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a first embodiment of an electromagnetic motorhaving a stepping rotor.

FIG. 2 is an elevational view thereof.

FIG. 3 is a sectional view of a detail taken along the line III--III ofFIG. 1, and

FIG. 4 is a plan view of a second embodiment of an electromagnetic motorhaving a stepping rotor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The stepping motor illustrated in FIGS. 1 and 2 comprises a rotor 1 madeof a permanent magnet and magnetized diametrically with respect to therotation axis of the rotor. The motor stator is constituted by twopieces 2 and 3, both of elongated shape and arranged side by side inmutually parallel disposition. The piece 3 constitutes the core of theenergizing coil 4 of the motor.

The piece 2 is a traversed by two feet 5, each situated in the vicinityof one of its ends and serving to secure and to position the piece 2 ona frame, which is not shown, for instance on the frame of a clockwork ormodule. The piece 3 is assembled to the piece 2 by a protrusion 3a, ofgenerally cylindrical shape. Protrusion 3a is engaged in a recess 6 ofcorresponding shape provided by an extension 2a of the piece 2. Thisprotrusion 3a is provided with a central hole through which passes ascrew 7 maintaining the heightwise location of said protrusion. Thepiece 3 at 3b is moreover traversed by a securing foot 5 determining itsorientation relative to the piece 2.

This manner of assembly of the two pieces 2 and 3 of the stator of themotor has the advantage of enabling the relative position of these twopieces to be determined with a high degree of accuracy. The two piecesare in the same plane, the plane in which is situated the axis of thecoil 4. Moreover, owing to their circular form, the surfaces in contactare perfectly engaged without there being any appreciable gap betweenthem. Finally, the two pieces 2 and 3 can be manufactured very cheaply,by a cutting and stamping operation.

At their opposite ends, remote from the protrusion 3a and recess 6, thetwo pieces 2 and 3 of the stator are each terminated by an enlarged poleface 2b or 3b, between which the rotor 1 rotates.

It is to be noted that, owing to the shape of the piece 3 of the stator,which has, at its two ends, only protrusions 3a and 3b which are oflittle consequence, it is possible to wind the coil 4 directly on thepiece 3. One could alternatively, in cases where the protrusion 3a issufficiently small, construct the coil 4 separately and independentlyfrom its core, then position the coil 4 on the piece 3 by passing itover the protrusion 3a thereof.

The motor represented in FIG. 4 also comprises a rotor 1, as in thefirst embodiment. The stator of this motor is made of two pieces 8 and9, which are elongated and arranged mutually parallel, the piece 9carrying the coil 10 of the motor. The piece 9 is terminated by an ear9a which provides a cylindrical recess 11, having a central axis,receiving a protrusion of corresponding shape 8a which terminates anextension 8b of the piece 8.

The enlarged pole faces of the two pieces 8 and 9 of the stator, betweenwhich the rotor 1 rotates, are designated by reference numerals 8c and9c, respectively.

Whereas, in the first embodiment, the two stator pieces 2 and 3 aresecured relatively to each other, after their assembled, relativeposition has been determined precisely, the piece 8 of the stator ismovable with respect to the piece 9 in the embodiment of FIG. 4. As amatter of fact, the protrusion 8a of this piece 8 is traversed by a foot12, securing the motor to the frame of an associated movement and aroundwhich the piece 8 can rotate. So far as the piece 9 is concerned, it isstationary, being fixedly positioned on the one hand by the protrusion8a of the piece 8 and, on the other hand, by a securing foot 13.

The enlarged pole face 8c of the piece 8 is provided with a fork-shapedportion, formed of two arms 8d and 8e, between which is engaged one arm,designated by reference numeral 14a, of a two-armed lever 14 articulatedat 15 on the frame of the movement. One can act on the second arm,designated by reference numeral 14b, of this lever 14 to bring the piece8 into one or the other of two stable positions. In one of thesepositions, piece 8 bears, by its fork arm 8d, against a stationaryabutment member 16 (position shown in FIG. 4), and in the other of thesepositions piece 8 bears by its fork arm 8e against a stationary abutmentmember 17. Each of these two positions corresponds to particulardirection of rotation of the rotor 1. A spring 18 acts to yieldablymaintain the piece 8 of the stator in the normal position shown in thedrawing.

The reversal of the direction of rotation of the rotor can be usefulwhen the motor is used in a timepiece where the user wants to modify theindicated time of a number of time zones by putting back the timeindicated by the clock clock.

It is to be noted that the position of the abutment members 16 and 17could also be adjustable, which would provide for the making of a fineadjustment in the eccentricity of the enlarged pole faces 8c and 9b withrespect to the axis of rotation of the rotor 1.

The general shape of each of the two motors disclosed and represented invery elongated which, when they are used in timepieces, enables them tobe placed between the supply battery and the periphery of the movement,in other words beyond the battery with respect to the center of themovement.

It is also to be noted that the securing means of the pieces of thestator described and illustrated could also be applied to the assemblingof stators made of three pieces, of the general type of the known motorspreviously mentioned. In this case the core of the coil could present,at its ends, two cylindrical protrusions respectively closely engaged inrecesses of corresponding shape presented by the two other pieces of thestator.

What I claim is:
 1. An electromagnetic stepping motor, comprising astepping rotor, and a stator which is made of at least two piecesassembled each to the other, one of said pieces presenting a protrusionof a general cylindrical shape and the other of said pieces presenting arecess of a shape corresponding to that of said protrusion, with saidprotrusion being engaged in said recess to maintain the assembly of saidpieces, the two pieces being dimensioned to provide for rotation of thetwo pieces around the central axis of the protrusion.
 2. Anelectromagnetic stepping motor according to claim 1, wherein said twopieces of the stator are both of elongated shape and are arranged sideby side in mutually parallel disposition, at adjacent ends thereof oneof the pieces providing said protrusion and the other of said piecespresenting said recess of corresponding shape and, at their oppositeends, each of said pieces having an enlarged pole face.
 3. Anelectromagnetic stepping motor according to claim 2, wherein one of thesaid elongated pieces constitutes a core for an energizing coil of themotor.
 4. An electromagnetic motor according to claim 1, wherein therelative position of said two pieces of the stator is adjustable byrotation of said cylindrical protrusion presented by said one of thepieces in said recess of corresponding shape presented by said other oneof the pieces.
 5. An electromagnetic stepping motor according to claim1, wherein said one piece and said other piece of the stator provide twoof three pieces which together constitute the stator of the motor andone of them passes through and provides a core of an energizing coil ofthe motor, the other of said three pieces being assembled with that oneof said two pieces which provides said core in a similar manner to thatby which said two pieces are relatively assembled by means of acylindrical protrusion engaging in a correspondingly shaped recess.